2 CHAPTER: Key Concepts and Important Questions
2.1 Introduction
This chapter introduces some of the key concepts on which much of contemporary rehabilitation practice and theory are based.The reader will find these points elaborated upon in different chapters of this book.
2.2 What is a successful rehabilitation project?
The Key here is to consider an appropriate time frame against which to measure the success or otherwise of a creek rehabilitation project. A creek rehabilitation project which looks great for even 10 years before reverting to its original state is no real success. When we are considering the success of a project we need to be thinking in a time frame of at least 100 years. Of course we can’t predict what external changes may impact on the area containing our rehabilitation project over time, but we should be designing every project with this time frame in mind.
The ultimate outcome that is being aimed for in all creek rehabilitation projects is a sustainable creek which is as close to original condition as is practicle. However the reality of achieving a compleate creek Restoration is in many cases simply not achievable. However while achieving a fully sustainable creek Restoration may not be possible the closer we can move towards this aim the better.
- A notional scale of desirability for a creek rehabilitation project could look like this:
- A Permanent* reduction in the rate of creek damage
- Permanently stopping ongoing damage
- A Permanent increase in creek stability and biodiversity
- Permanent and increasing levels of creek rehabilitation
- Restoration of original condition
As can be seen from the above scale even a creek rehabilitation project which permanently slows down the rate of damage occurring to a creek can be considered an improvement. However if a creek rehabilitation project is able to achieve a level where the creek is permanently, through the deposition of appropriate amounts of silt, increasing levels of biodiversity etc, moving closer to its original condition without requireing ongoing significant human input then it can be considered successful.
This level of sustainable improvement while difficult can and should be a desirable outcome for the majority of rehabiliation projects.
*Permanent can be considered to be 100+ years
2.3 The Importance of Encouragine Farm productivity
If the definition of genuine sustainability is “An equal and lasting balance between Society, the Environment and the Economy” then it becomes self evident that farmers and the “Greenies” are going in the same direction.
It is a little know fact that the Landcare movement which has over xxxx members in Australia and has spread to xxxx other countries around the world, was jointly initiated by the Australian conservation foundation and the National farmers federation. From as long ago, and in many cases before, the introduction of Landcare, Australia’s farmers have recognised, and been closely involved with, efforts to protect and enhance the Australian landscape.
In fact it is no exaggeration to say that no other single group of Australians have worked harder or contributed more to rehabilitation of Australia’s natural environment.
This commitment from Australia’s farmers has been largely because they understand in very real terms the importance of a sustainable landscape, not only for the productivity of their land but to the condition their land will be in, and the value it will have, years into the future.
The relationship between farmers and the “green movement” has not always been an easy one and probably never will be. However more than ever there is an increasing realization that sustainable landscapes, and in particular waterways, are good for farm productivity. And conversely what is good for long term farm is good for the environment.
2.4 Chain of Ponds
Prior to white settlement the natural way water in smaller water courses such as Creeks would move through the landscape was via a chian of ponds.
Prior to 1750, except in the hills and mountains, there were more marshes and fewer creeks than today.However where there was sufficient water to create an observable surface flow of water it often progressed though the landscape via a chain of ponds.
A chain of ponds is a situation where surface water steps downhill through the landscape. Instead of changing level in one continues flow, the natural form in the landscape is for the water to collect in larger individual ponds before stepping down over a relatively short distance, say 1 tenth of the pond length. This stepping down occurs either at a Riffle of gravel/stone in a Hard bed creek or via a Grassy shoot in a Soft bed creek.
There are multiple benefits provided by this natural way for surface water to move through the landscape; the ponds act as inertia pools slowing down the speed of the water that is flowing along the Creek, by slowing down the speed of the water erosion is minimised and slower water means that silts, often rich in organic mater and minerals, are more likely to be deposited, creating a positive feedback for local
biodiversity.
The chain of ponds also make a critical difference to biodiversity of the creek environment. Through creating a range of different environmental niches such as ponds of water, Green slides and riffles, a whole range of different species can exist and those species in turn allow other species to exist including carnivores, omnivores and herbivores.
2.5 Running Marsh
In Australia there are thousands of kms of new creeks where there were once Marshes. These New creeks have often become so incised that it would take hundreds of years of ideal conditions and silt deposition to fill them in to point where they once again had a profile similar to the original Marsh.
While it is in many cases impractical to attempt to recreate former marshes, due to the existence of a New creek, however it is possible through rehabilitation to make these creeks “marshier”. Marshy creeks or Running marshes so called because water moves through them more quickly than a traditional marsh, can be achieved through the appropriate use of vegetation and controls such as the exclusion of stock.
Successful rehabilitation projects employ techniques which can encourage changes within a New creek such as the recreation of a Chain of ponds. To recreate a Chain of ponds it is critical that there is a strong focus on the revegetation of the low flow channel with plants such as reeds, rushes and sedges.
Running marshes have other benefits besides those identified as occurring with the re- establishment of a chain of ponds. In a true marsh it often too wet for many trees and as a result the vegetation is often quite dense. In order to make creeks marshier it is desirable to make the creek as similar to a marsh as possible. A result of dense vegetation throughout the creek channel can be a substantial slowing down of the rate at which water not only moves through the creek channel but also the speed at which surrounding surface and subsurface water enters the creek itself.
Benefits of a Running marsh:
- Reduced water speed
- Reduced erosion
- Increased biodiversity
- Improved water quality
- Greater retention of sediments and organic matter
- A high density of rushes, reeds and sedges in the creek means that areas of erosion can be relatively quickly colonised and stabilised
Potential downsides to a Running marsh:
- As surface water move mores more slowly through a Running marsh than a New creek water can tend to back up in the Creek bed, raising the level and, depending on the depth of the creek channel, increasing the likelihood of flooding in the surrounding area.
- As a Creek becomes more marshy the way water moves through the creek will change.These changes in flow patens will quite likely lead to a changing paten of erosion as the creek adjusts to a new and altered albeit more stable morphology.
2.6 The Right Plant in the Right Place
The solution to more sustainable creeks starts and ends with the use of vegetation.Sure stock need to be excluded, primarily to protect the vegetation, and yes we need to minimize harmful inputs from areas adjacent to the creek environment, something a buffer zone of vegetation will assist with, but at the end of the day it is mostly about the vegetation.
Creek vegetation is relatively cheap, self sustaining, self replicating, flexible and provides a multitude of benefits.Benefits which range from supporting wildlife, cleaning water and stopping erosion to increasing farm productivity, improving human health and sequesting carbon.
While vegetation can do all the above mentioned things they all depend on one critical component, the right plant being planted in the right place. The wrong plant in the wrong place will die, or it will not successful reproduce, it will not stand up to the erosive effects of water flow or it will limit the range of biodiversity.
Putting the wrong plant in the wrong place can be throwing money away or worse creating a problem which is going to cost even more money to rectify.
2.7 Cluster Planting
In the past most planting has followed a fairly random patten with a wide range of species being mixed and therefore planted, together.
It is now considered desirable to plant significant numbers of the same species, 30-40, next to each other in a roughly square or circular patten. This number of 30-40 plants is considered appropriate for most species.
There are two situations where it is considered desirable to plant in clumps of 5-10 rather than 30-40.As eucalypts and other large trees can grow to have cannopies in excess of 20 meters clumps of 5-10 are considered appropriate.
The other situation where plants can be planted in clumps of 5-10 is in the low flow channel.There are 3 reasons for this 1) Typically the amount of space for planting in the low flow channel are more limited than in other parts of a creek 2) these plants are typically more expensive and 3) these plants typically reproduce far more quickly, and in greater numbers, and due to the water flow, also spread more widely.
For more information see Chapter xxxx
2.8 Access and Mainenance
One of the most significant changes in recent years is the aim to include functional access tracks where possible to rehabilitation projects. An access track is usually a graded path with a width of about 3 meters. For the access track to be most effective there are times when it is desirable for the track to enter the creek channel proper and not just run along the verge beside the creek channel.
The access track designed primarily for pedestrian access and definitely not for passenger vehicles.
The benefits of an appropriate access track include:
- Cost savings on the initial weed control works
- Cost savings during the planting phase of creek works
- Cost savings for ongoing weed and pest control
- Greater ease of monitoring the progress of the rehabilitation project over coming years
- An inducement to the landholder to regularly visit the creek to enjoy the benefits of the rehabilittion project
- A way for friends and other community members to appreciate the positive changes that are occuring in their local environment
For more detailed information see Chapter xxxx.
2.9 Some Important Questions and Answers
Qusestion:
Are damaged creeks really a problem?
Answer:
Consider the following:
- We live in the driest inhabited continent on the planet
- No water means no life
- 90% of the water we use in rural or urban situations originates in creeks
Damaged creeks are so widespread in Australia that for many of us damaged creeks and creek systems are all we know. Because damaged creeks are so common, and the work required to rehabilitate them so great, and costly, it is not unreasonable to ask why not just leave them the way they are? Is it really such a problem to leave them as they are?
Qusestion:
"Erosion doesnt look that great but creeks are always eroding, it is just a natural part of the cycle!”
Answer:
While erosion is a natural part of the life cycle of creeks and waterways, it is the degree of erosion and the type of erosion that is important. Excessive erosion results in a multitude of problems; the loss of fertile land, the loss of biodiversity, the loss of infrastructure such as fences and bridges, the smothering of down stream properties and the sedimentation of the water and water storage areas such as reservoirs.
Qusestion:
“Sure if we put creeks back like they were there would be more native wildlife but we don’t eat things that live in creeks so what does it really matter if there are few less dragon flies and kookaburras?”
Answer:
There are two parts to this answer; the first is a persons individual opinion on whether other living things have a right to exist and be supported.
The second answer is more pragmatic.It is a reality that humans live in and are dependant on the natural living environment. That dependence is not only about what we can immediately eat, it is about bees that pollinate crops, Vegetation that shelters stock and protects soil, organisms that stop soil becoming sterile and break down waste matter, birds that consume insects, biodiversity even plays a critcal role in recreational persuits and the physical and mental health of the community.
Qusestion:
"Why worry about exotic vegetation? Sure blackberries have thorns but the fruit tastes nice and willows provide nice green shade and so what does it matter if a plant is exotic or not?”
Answer:
Exotic vegetation has not evolved in a local Australian environment and therefore is not compatible with the intricate web of life of a particular local Australian landscape. The result is that if the exotic plants thrives, as often they do because they have no natural predators, they will come to dominate a local environment which in turn will lead to an often dramatic loss in biodiversity.
Qusestion:
"What does it matter if the water that comes out of creeks dirty? The government will treat water with chemicals to make sure it is clean before we drink it”
Answer:
When talking about water quality many people only think in terms of man made chemicals, such as herbicides, which may be polluting the water.However there are a range of different ways in which water quality can be lost:
- Artificial chemicals
- Excessive nutrients
- Harmful bacteria
- Excessive levels of silt
- Lack of oxygen
Any one of these forms of pollution can cause a loss of biodiversity, damage to stock and in some cases effect the health of humans.While many of the forms of pollution listed above can be negated, at a cost, through the use of a range of chemicals, this will not stop the damage that polluted water can do before it is treated.
It is also worth noting that one of the seemingly least “offensive” pollutants, silt, can actually be the most damaging and costly to rectify.Excessive silt loads can not only smother an extensive range of living organisms downstream, impact on the well being of stock drinking from the water source but longer term excessive silt loads can lead to the reduced capacity, and increased evaporation, in dams and reservoirs including those that provide us with drinking water.
Qusestion:
“Isn’t a creek really just a channel to carry water, does it matter if it is eroded or there is no plant life in it? In fact the fewer plants the more water for us!"
Answer:
The key to this question is how much of the water is available for use, by both humans and the natural environment in total?
In Australia water flow in creeks, and as a result in rivers, is highly variable.In a high flow event most of the water entering a heavily eroded creek can flow through the system and out to sea in a couple of days leaving the creeks dry.
Compare this with a historical situation where the morphology of the waterway including the vegetation layer, significantly slowed down and absorbed the water.
Most of this water was not lost from use rather it simply moved through the waterway system over an extended period of time.In this way waterways which rather than drying out in days or weeks could continue to have running water for much of the year.
It has been calculated that in fact there is an actual net gain of available water for harvest from a natural waterway compared to an equivalent highly eroded waterway.
Consider a 2m length of metal downpipe cut in half length wise.If we take one half of the pipe and point it towards the ground on a 45 degree angle and then pour in 2 litres of water in at the raised end, the water will be shoot down the pipe in seconds.Place a sponge in the length of the half downpipe and now pour in the water.Obviously the water will take much longer to pass down the pipe and will probably still be dripping hours later.
Qusestion:
Hydration of the landscape? I don't even know what that is!"
Answer:
Hydration of the landscape relates to the amount of water, often subsurface water that exists on and in the landscape. It is quite common for a New creek to become so incised that the bottom of the creek cuts its way to a point below the water table.When this happens it is a bit like pulling a plug out of the bath.The creek starts acting as a gutter and the water table drains away into it.As the water table is drained additional water that may be in the surrounding landscape gravitates into the water table and is in turn drained away.In this way it is possible for a landscape that may have held the water for many months, supporting a range natural and farm actives to quickly vanish.